Fabrication of concrete elements or structures



C. DOBELL Jan. 7, 1947.

FABRICATION OF CONCRETE ELEMENTS 0R STRUCTURES 3 Sheets-Sheet 1 Filed Oct. 13, 1943 I I d I I I I I I r I r I I I INVENTOR CURZON ATTORNEYS 7 FABRICATION 0F CONCRETE ELEMENTS 0R STRUCTURES c, DOB-ELL 3 Sheets-Shoot 2 Filed o tl 13, 1943 INVENTOR cunzcn ooBELL I'TORNEYS rill. V/II/l/l/l/l/l I. i

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PATENT orn ca R STRUCTURES Curzon Dobell, NewYork, N. Y. Application October 13, 1943, Serial No. 506,074

1 v 19 Claims. This invention relates to the fabrication of 1118 strength concrete elements or structures by a continuous process which has a wide range of use ful application.

The more important, objects of the invention may be summarized as follows:

1. To provide a continuous fabricating process whereby high strength concrete elements or structures of great length'or-height may be rapidly and economically fabricated. in situ or otherwise, with the aid of relatively short moulds of comparatively simple and inexpensive design.

2. To provide for the building of high strength .concrete elements or structures in situ upon or against a preformed structure by a continuous process of fabrication which enables said me formed structure to be economically used as part of the construction apparatus.

3. To provide for the fabrication of high strength concrete elements or structures by a continuousprocess which enables the strength of the concrete in successively formed sections of such elements or structures to be selectively controlled without changing the thickness or size of said sections.

V 4. To provide for the fabrication of high strength'concrete elements or structures by a continuous process in 'which the concrete is subjected to high pressure which is utilized toeifect rapid removal of excess water from the concrete and thereby speed up the transformation of the concrete from aplastic to a granular condition during passage of the concrete through a relatively short mould or form.

.5. To provide for the fabrication of high strength concrete elements or structures of great mass by a continuous process in which excess water is qulckly expelled from the interior as well as from outer portions of the mass in such manner as to ensure the rapid development of uniform strength characteristics throughout the entire mass.

6. To provide forthe fabrication, in situ, of

high strength concrete elements or structures of considerable height by a continuous process which requires little or no scaffolding.

7. To provide for therapid, economical and convenient fabrication of concrete structures by a process which enables floors. beams. roofs or other elements of a structure to be first fabricated at ground or other convenient low level and then progressively raised to their final positions by continuous and progressive fabrication of their supporting walls, columns or other supporting structures.

.8. To provide for the fabrication of a high strength concrete structure upon or against a preformed structure by a continuous process which. simplifies the development of continuity o between the two structures.

9. To provide for the fabrication of high strength concrete elements or structures by a continuous process, which lends itself to the fabrics.- tion of solid, hollow, or cellular elements or structures oi' anv desired height, length, shape or cross section. i

10. To provide for the fabrication of high strength concrete elements or structuresby an extrusion process in which pretensione'd and/or 16 passive reinforcement members are progressively embedded in the concrete during fabrication thereof.

11. To provide for the fabrication, in situ, of high strength concrete elements or structures of 20 considerable height by a continuous process which may be carried out with the aid of relatively short moulds or forms and with little or no scaffolding and in which provision'is made for incorporating passive and/or pretensioned reinforcement mem- 28 hers in the concrete during its passagethrough the mould or moulds.

12. To provide for the fabrication of high strength concrete elements or structures by a continuous process in which the concrete is forced 30 through a mould unclera pressure which is determined, at least in part, by controllable tensiOn produced in reinforcing members embedded v in the concrete during its passage through the mould.

13. To provide for the fabrication of high' strength concrete elements or structures by a continuous process in which the concrete is forced under pressure through a mould and in which the pressure of the concrete is utilized to stretch 40 and tension reinforcement members embedded in the concrete during its passage through said mould.

14. To provide for the fabrication of high strength concrete elements or structures by a continuous process in which the concrete is forced under pressure through a mould and in which reinforcement members. pretensloned to a predeter- 'mlned degree, are embedded in the concrete during its passage through the mould, the maximum extent to which the reinforcement members are pretensioned being controllable independently of the tensioning pressure of the concrete. X

Other objects, advantages and characteristic features of my invention will be apparent from the following description of the several. referred embodiments illustrated in the drawings, in which- Fig. 1 is a longitudinal sectional 'view of one form of apparatus which may be used in fabrieating concrete elements or structures by a continuous process embodying the principles or my invention.

aohtimhal y provided with packing glands Ii through which reinforcing wires i2 and i3 are passed into the mouldwhere the inner ends of said wires are fastened to a movable starting head H by suitable wire clamps l5. Thewires l2 are passed inwardly through the packing glands II from Fig. 2 is a transverse sectional view taken substantially along the line 2-2 of Fig.- 1.

Fig. 3 is anenlarged fragmentary transverse sectional viewot the mouldfishown in Fig. 1. Fig. 4 is an enlarged longitudinal sectional view of the starting head employed iniconjunction suitable supply reels 16 which may be arranged in any suitable manner. .In the present instance the 'reels i6 areshown .carried by supporting strutsnl'l extending from one end of mould l.

The reels l6 are preferably tension. regulating reels from which the wires l2 are paid out only qafter these wires have been stretched and ten- .with'the mould shown in the preceding figures.

Fig. 5 is a view similar to Fig. 1, but showing themould e ipped with pulling and'retarding means for controlling the movement oi'the 8350;!

ciated starting head.

Fig. 6 is a view similar to Fig. 1, butsl iowing the mould equipped with retarding means for I retarding therate of movement of the starting head and the concreteas' theseelement's-emerge from the discharge end of the mould.

Fig. '7 isa'view illustrating one application or my invention whereby a mould; such as'shown in Fig.1, maybeutiiized for iab'ricatinga concrete element or structure'insitu upon a previously from the Dretensioned fabricated concrete structure'in such manner as r to fenable'the previously fabricated structure to be employed as part of r the construction apparatus.

Fig. 7a is a transverse sectional view taken sub stantiallyalong thelineld-la'ot Fig. V

Figs. 8.' 9 and 10 are'vertical'sectional views illustrating a further application of my invention whereby partsofa structure may be fabricated at ground or other convenientlow level and then raised .to their final position by'prog'ressive fabrication" of their supporting walls." columns; or other supporting structures. a Y v a Fig,# 11 is] a sectional-view of a ;modified type ofjdomejwhich may'beused in connection with the apparatus shown" in- Figil to drain surplus water vfrom'the interior a's'well as from the outer portions ofthe mass. A .Fig'. 12 is a sectionalview taken along the line .|2.=-l2'.0f Fig. 11.

, Figs. 1 to .4 inclusiveillustrate' one -'form;of apparatus which may be used in" accordance with my. invention for the manufacture of ricating. process.- In ,this case the mould '4, through which the concrete is pumped under pressure, comprises a cylindrical outer shell '5 designed to withstand internal pressures which may be in excess of,2,000 lbs; per square inch. In mostcases, however,jthe internal pressures to which the-shell is subjected in service will be lower their 1000 lbs. per "square' inch. Theshell 7 may be made of any suitable material and-is provided with a lining consisting of metal staves 6 arrangedin circular series. The cross sectional shape ofeach' stave 6 is'simiIar to that of an I-beam, the outer flange 'l-being' somewhatfwider than, the inner flan e v8, to facilitate arrangement or thestaves'in circul'ar'series with corresponding flanges of adjacent staves butted togetherin edge to edge relation.

The mould space bounded bythe inner flange of thestaves is closed at one end by ahollo'w h? strength, reinforced concrete by a continuous fabsioned-toa predetermined degree by the pulling and stretching action to which the wires are subjected as hereinafter described. This ensures that the wires, i2 will be embedded in the concrete -resist;,turni ngl. movement of the reels until the wires ilhave been stretched and tensioned to a predetermined degree. 1 The-startingheadjll is initially positioned close to-theinnerend of dome 9 and is guided, during part of its-travel. bythe surrounding staves 6.

' The end of the starting headnearest the dome is covered by a compressible gasket 19 and a metal plate 20 securedin place by screws or nails 2|. The,:plate,20 is free to move against the gasket viiito compress the latter againstthe adjacent endoi'the starting head. The gasket I9 is made of rubber'or, other resiliently compressible mate- 'rial'which iscapable oi substantial lateral expansion when subjected to compression between the plate 20 and the starting head M. A leather packing ring 22 is secured to the starting head so that'it surrounds, and projects beyond the gasket l9 andthe plate 20. This packing ring is iorce'doutwardly into sealing engagementwith the inner flanges 801 the staves 8 by the aforesaid lateral expansion of .the gasket I9. ,This prevents any possibility of the mortar in the concrete being squeezed between the starting head and the surrounding staves. The packing ring 22 :is secured to the'starting head by nails or screws n. -The. starting head 14, gasket I9 and plate 20 -are provided with suitable holes 24 through which crete by use. of the apparatus shown inFigs. 1

dome 9 which is open at'its inner end and is weld- .ed or otherwise secured to saidflange's. The interior'of dome 9 is connected, by pipeconnection ill, to the delivery side of a conventional concrete pressure pump (not shown) Dome 9 is also the wires l2 and I3 are passedto the clamps iii.

The fabrication of prestressed, reinforced con-' to 4 inclusive is accomplished in the following manner: Plastic concrete is pumped, under suitable pressure (usually not substantially less than 2001lbs. per square inch) through pipe connection l0 into domefl and against plate 20 of starting head .1 The pressure of the concrete against the starting head H stretches and tensions the reinforcement wires I2 andresults in the starting head being forced toward and through the open end of the mould at a rate which is controlled, in part, by the effective pressure of the concrete and, in part, by the setting of the tension regulating means governing the paying out or the wires i2 from the reels I6. In this parstaves.

ticular instance the pressure of the concrete acting against the starting head I4 is utilized to stretch and tension the wires l2 so that the latterare embedded in the concrete in a pretensioned condition during passage of theconcrete through the mould 4. At the same time successive lengths r of the untensioned wires I 3 are drawn through. a

the mould by the travelling movement of the starting head VM and embedded in theconcrete to serve as passive reinforcement.

As the leather packing ring 22 of the starting head moves away from the dome 9 the concrete on the concrete, practically all of the water in excess of the amount required for hydration is expelled from the concrete through the Joints formed by and between said flanges, it being understood that thesejoints are of such a nature as to permit water to be forced through them under a pressure and into'the open-ended drain passages comes in direct contact with the inner flanges 8 r of the metal staves and, owing to the pressure movement of the starting head independently of the pressure of the concrete in the mould.

A simple form of mechanism capable of being I used either as a starting head pulling or retardmg means is illustrated in Fig. 5. This mechanism comprises a feed screw 30 which is attached to the starting head bya plate 3| and is slidable 28 separating the web portions of the metal the mould 4 permits the concrete to set rapidly and to develop exceptional strength in the short time required for it to travel fromthe dome 9 to the opposite or discharge end of the mould.

The starting head I4 is needed only at .the' commencement of the fabricating process to en- 'I'his pressure expulsion of excess water from the concrete through the drainage system of through a guide opening provided in a cross-head 32 carried by supporting members 83 attached to the mould 4. The feed screw carries nuts 34 119.26 38 arranged at opposite sides of the crossa When the pressure necessary to develop the desired strength in the concrete exceeds that required to produce the desired tension in the reinforcement members 12, the nut 34 is positioned sure the proper tensioning and feeding of the reinforcement wires l2 and I3 and the development of the requisite back pressure on the concrete initially supplied to the mould. By the time the concrete reaches the discharge end of the mould it has set sufficiently to become bonded to the:

reinforcement members 12 and I3 and therefore takes over the work of pulling these members through the mould, .The requisiteback pressure on the concrete travelling through the mould is also developed independently of the starting head soon after the commencement of the fabricatin process. It will be apparent that forward movement of the concrete is resisted through resisting of forward movement of the reinforcement members which are attached initially and indirectly to the forward end of the concrete through the starting head 14 and thereafter become directly attached or bonded to said forward end as the concrete sets, such action'serving the double funcexpell the surplus water and to place the reinforcement under tension. I

The foregoing method of using the apparatus shown in Figs. 1 to 4 inclusive enables exceptionally high strength prestressed reinforced concrete elementsor structure of indefinite length to be manufactured by a continuous fabrication process with the aid of a mould of relatively short length. By regulating the pressure on the con.-

' tion of compressing the concrete to densify it and against the adjacent side of cross-head 32 and the nut 35 is backed oil a suitable distance from the opposite side of the cross-head. During the fabricating process the nut 34 is rotated in contact with the cross-head and in the direction necessary to permit the feed screw and the starting head to be forced toward the discharge end of the mould'at' retarded rate of speed by the pressure of the concrete acting against the starting' head. In this case the rate of'travel of the starting head is determined by the speed of ro tation of the nut 34. In practice the nut 34 will preferably be operated by worm gearing or other operating means capable of regulation to turn the nut at any speed necessary to produce the tension desired in the reinforcement members l2.

When the pressure necessary to develop the I desired strength in the concrete is less than that required to produce the desired tension in the reinforcement member 12, the nut 35 is positioned against the cross head and the'nut 34 is backed an appropriate distance from the crosshead. The nut 35 is then rotated in contact with the cross-head in the proper direction and at sufilcientspeed to cause the feed screw 30 and the starting head 4| to travel toward the diecrete during its passage through the mould itjis possible to control the strength developed 'by the concrete in the short time required for it to travel from the dome 9 to the discharge endof .the mould. Insofar as certain features of the invention are concerned, the reinforcement members may be omitted entirely or may be embedded in the concrete in either a passive or a pretensioned condition. In some cases'all the reinforcement members may be embedded in the concrete in a passive condition while, in other cases, all

the concrete in a pretensioned condition'.. In

certain cases where the main consideration is the continuous fabrication of high strength conthe reinforcement members may be embedded in form.-

charge end of the mould more rapidly than would be the case if these parts were being moved by the pressure of the concrete in the In Fig. 6 I have shown another form of mechanism which may be used for regulating the tensionlng of the wires H by retarding the movement of the starting head and the fabricated concrete as: they emerge from the open or discharge end of the mould. In this case the emerging starting head or concrete, as the case may be, is engaged by pressure applying retarding shoes 31 which aremovably supported by suitable supporting members 38 so as to be capable of movement in a direction at right angles'to the axis of the mould. The shoes 8! are pressed against the starting head or the concrete by pressure applying springs 30 the loading of which may be regulated by operation of suitable adjusting screws 40 which are threaded through a supporting ring 4| and are provided, at their inner ends, with spring seats 4? bearing against of mould 4 by suitable supporting arms 43 or. inany other desired manner.

Another application of the invention is illustrated in Flgl' 7. In this instance the, extruded concrete structure is built in place upon a previously formed structure which is used as part of e the construction apparatus. The built-in-place' structure is indicated at 45 and lshere shown as a simple column or pole erected on a preformed base structure 45 which may represent either a foundation or a precast base section of the. column or pole. The structure 45 is built in situ by pumping concrete upwardly through a cavity 41 of the base structure 45 and through a relatively short vertically disposed mould 4 which, except for the omission of the Home 9, is exactly the same as the mould 4 described in connections with Figs. 1 to 4 inclusive. In this case the mould 4 is tied to the base structure 46 by anchor bolts 48 having their lower ends embedded in said structure,'said bolts extending upwardly between the staves 5 of the mould 4 and being equipped at their upper ends with stave-engaging washers 45 and clamping nuts 55. The concrete is-pumped into cavity 41 through a pipe 52 having an upwardly curved inner end 53 opening into the bottom'of said cavity. The outer end of pipe 52 is provided with a. T-connection 54 having one branch connected, by pipe connection 55, to the delivery side of a concrete pressure pump (not shown). Another branch 58 of T-eonnection 54 is fitted with a packing gland 51 through which is passed a reinforcing wire l2 which is fastened tothe starting head H by a clamp IS in the same manner as described in connection with the reinforcement wires i2 shownin Fig. 1. e

As the starting head l4 (Fig. '7) is forced upwardly it serves to tension the wire l2 which is paid out from a tension regulating reel such as that indicated at IS in Fig. l. The starting head and the concrete beneath it will continue to travel upwardly as long as concrete is pumped under pressure through the pipe connection 52 so that a pole or column of a y foundation structure 46, and will be tied to such structure by the concrete filling left in the cavity 41 and also by the pretensioned reinforcement member I! which, in the completed structure, is-

cavity v4! through any desired arrangement of passages provided for this purposes so that they,

may be located in the completed structure in any desired manner.-

In those cases in which it is desired to produce a ring-shaped or annular concrete structure such as an annular wall or pipe it is obvious desired height, within practical limits, may be erected in situ .upon the member movable between the inner and outer series of staves. In all other respects, however, thelannular or ring-shaped mould willbe substantially the same as the mould shown in Figs.

-1 and 7. As a matter of fact, the shape of the mould is not acritical factor since it will nat- .urally be varied according to the shape of the concrete element or structure to be produced in accordance with the principles of my invention.

Figs. 8, 9 and 10 illustrate a further application of the invention whereby floors, beams, roofs or other elements of a structure may be fabricated at ground or any other convenient level andthen raised to their final position by progressive fabrication of their supporting walls,

columns or other supporting structure.

In describing the illustrated example of this last mentioned application it will be assumed that the structure to be fabricated is a circular concrete tank. The foundation 80 is first fabricated as a precast structure'provided with an annular mold forming cavity 6| extending downwardly from the upper surface thereof and with any suitable number of curved passages 52 extending from the bottom of the cavity to the outer side of the foundation, each passage 62 being connected, by suitable pipe connections 63, to the discharge side of a concrete pressure pump (not shown) or to a header to which concrete is pumped under pressure by said pump.

Each annular wall of mould cavity 6| is provided with a drainage lining consisting of a cir cular series of staves 65 corresponding to the poSed between the outer flanges of the staves and that the mould] shown in Figs. 1 and 7 maybe replaced by moulds of annular form; that is to.

say, moulds comprising spaced inner and outer metal staves 6. When annular moulds of this type are used it is necessary, of course, that the starting head be also constructed as an annular the adjacent side wall of the mould cavity. The anchor bolts 65 correspond to the previously mentioned anchor bolts 48 and have their lower portions embedded in-the foundation 60. The inner flanges of each'series of staves 65 are initially covered by thin liner plates 68 which are displaceable as hereinafter described. A vertically displaceable pallet 10, made of metal or any other suitable durable material, is initially arranged at the bottom of the mould cavity Bl so that it covers the upper ends of the passages 62. This pallet is provided with openings through which tensionable reinforcement members, here shown as steel .wires II, are passed upwardly into the mold cavity Bl. The wires Il may be led to the mould cavity 6! through the pipe connections 63 and passages 62 or in any other suitable manner, said wires being paid out from tension regulating reels such as those described in connection with Fig. l or from any other tension controlling means. The opening in the pipe connections 63 through which the wires II are passed to the mould cavity 6| are provided with suitable packing glands l2.

In the use of the construction apparatus shown in Figs. 8, 9 and 10, concrete is first poured into the mould spaces bounded by the inner and outer liner plates 68 to form an annular wall section 14 resting on the pallet 10, said wall section being bonded to the portions of the reinforcement wires 1| extending above said pallet. A concrete the pallet III. As this concrete rises in the mould space bounded by the liner plates 68 it causes the pallet 10 and the wall section 14 to be progressively raised, as indicated in Figs. 9 and 10, to any desired height. The liner plates 68 move upwardly with the wall section 74 and the pallet 10 until they are raised clear of the mould and are free to drop away or to be removed from the wall section 14. the remaining portion of the tank wall by pumping concrete upwardly through the mould continues until a wall of the desired height is obtained. The pressure on the pumped concrete and the drainage of water therefrom during passage of such concrete through the mould may be so regulated in relation to the length of the mould as to ensure that the pumped concrete will set and acquire the requisite strength by the time it reaches and commences to emerge from the top of the mould.

In connection with Figs. 8 to 10 inclusive, it will be understood that a floor, horizontal beams or girders, or any other'type of superstructure, may be superimposed on and Joined to the 'wall section 14 before the latter is raised by the pressure of the concrete which is pumped to the mould through the passages 62' provided, of course, that the weight of the superstructure is within the lifting capacity of the apparatu as measured by the pressure of the pumped concrete on the pallet 10 less the friction of the mould and the tension in the pretensioned reinforcement members II.

It will also be understood that the principles of construction exemplified by the showing in Figs. 8 to 10 inclusive may be applied in a variety of ways dependent upon the type of concrete structure to be erected in accordance therewith. It is possible, for example, to provide a series of moulds in which the upper sections of supporting members, such as posts or columns, are first precast and then raised to their final position by forcing concrete upwardly through the mould to progressively form the remaining portions of the length of said columns, posts, or other supporting members. Obviously, the number, shape and details of the moulds used for fabricating different types of concrete structures in accordance with the principles of my invention will vary accord ing to the design of the structure to be erected and other conditions which must be taken into consideration.

When fabricating vertical structures such as those illustrated in Figs. 7 and 8 it is feasible and, in some cases, may be necessary or desirable to progressively increase the pressure on the concrete in the mould as the structure rises vertically. Thus, the pressure to which the concrete is subjected in forming the first section of 'the structure .in the mould may be progressively increased so that each succeeding section will have greater density and strength than the preceding section. In this connection it will be understood that the progressive increase of pressure here referred tomay be greater than that which is necessary to carry the increasing load due to the increasing height and. weight of the structure which is being fabricatedand raised. In this way it is possible to increase the strength of the concrete in succeedng sections of the structure which is formed in the mold without increasing the size and thickness of the sections. In other words, the

This progressive fabrication of when the principles 01' my invention are applied to the continuous fabrication of concrete elements or structures of great mass it is possible that the time required for expelling excess water from the concrete through the drainage openings provided by the staves lining the inside of the mould will be so great that the rate of manufacthe staves may be so high as to make it impossible to maintain the requiredmovement of the concrete through the mould. This difliculty, however, may be overcome in various ways by providingsuitable means for draining excess water from the interior of the concrete mass. For example, in the case of an apparatus such as shown in Fig. 1, the dome 9 may be provided with suitable bleeders I1 (Figs. 11 and 12) through which excess water is drained from the interior portion of the mass of concrete supplied to the mould. As here shown each of these bleeders consists of four segments 18 fitted together to form, in effect, a. cylindrical bar, the inner corners of the segments being champered off to provide a central drain bore 19. Inv this case excess water is forced from the concrete mass into the drain bores of the bleeders through the inner ends of said bores and through the joints formed by and between the segments 18 which are suitably fastened to the dome 9., If

it is desired to pass the reinforcing wires 12 and I3 into the mould through the bleeders. this may be accomplished as shown in Fig. 11, it being noted that the wires are passed through packing glands located at the inner ends of the bleeders. In this case most of the water draining into the bores 19 of the bleeders is forced through the joints formed by and between the segments 18 of each bleeder. If it is desired to have the bleeders open at both ends the wires may be carried through the dome 9 by means of separate packing glands as shown inFig. 1.

Having thus described my invention, what I claim is:

1. The fabrication of vertical concrete elements or structures of considerable height by a continuous process comprising extruding concrete upwardly through a short vertical mould associated with a preformed concrete structure to thereby fabricate an extruded concrete element extending a substantial distance above said mould and having its base portion bonded to and supported by said preformed supporting structure.

2. Apparatus for use in making high strength concrete elements or structures by a continuous fabricating process comprising a mould, means for forcing concrete under pressure through said mould, a travelling starting head initially arranged in said mould in the path of movement of the concrete from its point of entry to it point of discharge from said mould, said starting head comprising a body portion, a movable pressure plate carried by said body portion and against which the concreteis extruded, a asket interposed between said body portion and said plate and made of resiliently compressible material capable of substantial lateral expansion when subjected to compression between said plate and said body portion, said plate being movably connected to the body portion so that it is moved toward and relatively to the body portion by the pressure of the concrete extruded thereagainst and thus serves to effect compression and lateral expansion of said gasket and a packing ring carried by said body portion and encircling said plate and gasket, said packing ring being adapted to be forced outwardly into sealing engagement with the surrounding wall structure of the mould by the lateral extension of said gasket and reinforcing elements extending into said mould and anchored tending into said mould and anchored to the to the body portion of said starting head so that successive lengths of the reinforcing elements are drawn into and through said mould by-movement of said starting head toward and'through the concrete discharge opening of the mould,

said reinforcing members being thereby embeddedin said concrete as it passes through the mould. I

8. The method of fabricating a concrete pole or column which comprises forming the base section of the pole or column with an internal through passage extending downwardly from the top of said section and then completing said pole or column by extruding concrete upwardly through said passage.

4. The method of fabricating concrete building structures or elements which comprises initially fabricating a precast concrete section with a through passage, arranging a relatively short mould against a surface of said section so that one end of said passage opens into said mould, extruding concrete through said passage and said mould to thereby fabricate a further extruded section of the concrete structure or element in situ against the initially fabricated precast section, and draining water from the extruded concrete during its passage through the mould so that the extruded concrete is transformed from a plastic to a high strength granular mass by the time it reaches and commences to emerge from the mould.

5. The method of fabricating concrete building structures which comprises initially fabricating a precast concrete foundation'with a mould cavity extending downwardly from the upper surface thereof and with internal passages extending from the bottom of the mould cavity. to an external surface of the foundation, arranging a movable pallet on the-bottom wall of the cavity so that it covers the ends of the passages opening into said cavity, introducing concrete into said cavity through the top opening thereof to thereby form a. moulded concrete section adapted to occupy an elevated position in the finished structure, arranging movable liner plates in said cavity prior to the aforesaid introduction of concrete therein to thereby prevent bonding of the introduced concrete to the defining walls of the cavity and then extruding concrete through said passages and cavity to raise said concrete section to its final position and to simultaneously form an extruded supporting structure for said section.

6. The method set forth in claim 5 which in- 'cludes the step of passing the leading ends of long lengths of reinforcing members into said mould cavity prior to the initial filling of the cavity to form said concrete section whereby said leading end portions of the reinforcing members are bonded to said section so that, during subsequent raising of said section to its final position, successive lengths of the reinforcing members are drawn into said cavity and are bonded to the extruded concrete during its passage through said cavity.

7. Apparatus for use in making high strength concrete elements or structures by a continuous fabricating process, comprising a mould through which concrete can be extruded under pressure,

8. Apparatus for use in making high strength concrete elements or, structures by a continuous fabricating process, comprising a mould through which concrete can be forced under pressure, a travelling starting head adapted to be initially arranged in said mould in the path of movement of the concrete from its point of entry to its point of discharge from said mould andadapted to cooperate with reinforcing elements extending into said mould and anchored to the starting head so that successive lengths of the reinforcing elements are drawn into and through said mould by movement of said starting head toward and throughthe concrete discharge opening of the mould, tensioning means from which the reinforcing elements are passed to said starting head, and means engageable with the starting head to retard the travelling movement thereof toward the discharge end of the mould.

9; Apparatus for use in making high strength concrete elements or structures by a continuous fabricating process, comprising a mould through mould, tensioning means from which the reinforcing elements are passed to said starting head, and means operable to increase the speed of travel of the starting head toward the discharge end of the mould.

10. Apparatus for use in making high strength concrete elements or structures by a continuous extrusion type fabricating process, comprising an extrusion mould through which concrete can be extruded under pressure, through said mould,- said mould being provided with a drainage lining through which excess water is drained from portions of the concrete adjacent said lining, and means extending into the interior of th mold and having a passage therethrough for draining water from the interior of the concrete mass during its passage through said mould.

11. A method of fabricating high strength concrete structures, which consists in extruding concrete under pressure through a mold, and simultaneously therewith placing the moving concrete in the mold under predetermined increased pressure forcing surplus water therefrom by resisting at its forward portion normal passage of the concrete through the mold, thereby facilitating the setting of the concrete and increasing its strength.

12. A method of fabricating high strength concrete structures, which consists in extruding conc'rete under pressure through a mold, and simultaneously therewith placing the concrete in the mold under predetermined increased pressure forcing surplus water therefrom by resisting forward movement of the concrete at its forward end through the action of resisting forward movement -of reinforcement attached to said forward end of the concrete and extendin rearwardly therefrom through the mold and said mixture, thereby facilitating the setting of the concrete and increasing its strength.

13. .A method of fabricating high strength reining the tensioned reinforcement to the concrete as they emerge from the mold, thereby facilitating the setting of the concrete and placing the extruded concrete under permanent compression. 1 14. A method of fabricating high strength reinforced concrete structures, which consist in extruding wet plastic concrete together with steel reinforcement under pressure througha mold, said reinforcement being attached to the forward end of the concrete as it emerges from the mold and extending rearwardly therefrom through the mold, simultaneously therewith tensioning said reinforcement and increasing the extruding pressure on the concrete by placin a, predetermined restraint on the movement of the reinforcement at a point rearwardly of the mold and utilizing the extruding action of the concrete simultaneously to tension and draw the reinforcement through the mold against such restraint, whereby forcing excess water from the concrete and outwardly of the mold, and bonding the concrete to the tensioned reinforcement as they exit from the mold, thereby facilitating the setting of the concrete and placing the extruded concrete under permanent compression.

' 15. A method of fabricating high strength reinforced concrete structures, which consists in extruding concrete together with steel reinforcement under pressure through a mold, said reinforcement being attached to the forward end of the concrete as it emerges from the mold and extending rearwardly therefrom through the mold, simultaneously therewith tensioning said reinforcement and increasing the extruding pressure on the concrete by restraining movement of the reinforcement at a point rearwardly of the mold and utilizing the extruding action of the concrete to draw the reinforcement through the mold against such restraint, modifying the extruding pressure required and the resultant density and strength of the extruded concrete by applying external force to said forward end of the concrete in a direction longitudinally of the mold, and bonding the concrete to the tensioned reinforcement as they exit from .the mold, thereby facilitating the setting of the concrete and placing the extruded concrete under permanent compression.

16. The method defined in claim 15 in which said external force is applied in a direction opposing forward movement of the concrete, thereby increasingthe density and strength of the extruded concrete.

17. A method of fabricating a high strength concrete structure in situ on and against a preformed concrete structure, which consists in preforming a concrete structure with a cavity therein open to' the side thereof on which the high strength structure is to be fabricated, associating an extruding mold with the preformed structure at said cavity, and forcing concrete under pressure into the cavity and outwardly through the mold.

18. The manufacture of concrete elements or structures by a continuous process, comprising continuously extruding the concrete through a mold under pressure forcing excess water from and densifying the concrete, and gradually varying said pressure during passage of the concrete through the mold to thereby modify the density and strength of successively extruded portions of the concrete.

19. The manufacture of concrete elements or structures by a continuous process, comprising continuously extruding concrete together with reinforcement through a mold under pressure forcing excess water from and densifying the concrete, applying said pressure to a tensioning of the reinforcement as it passes through the mold, gradually varying said pressure during passage of the concrete through the mold to thereby modify the density and strength of successively extruded Certificate of- Correction 1 Y Patent No. 2,413,911. 4 January 7, 1947.

OURZON DOBELL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 7, line 62, for the word purposes read pur ose; column 12, line 58, claim 10, strike out the words and comma.

through said moul and that the said Letters Patent should be read with thcse ggirections therein that the same may conform to the record of the casein the Patent e Signed and sealed this 25th day of March, A. D. 1947.

LESLIE FRAZER,

First Assistant Commissioner of Patents. 

